Read the extract given below and answer the questions that follow:

You are wel", Sadao agreed. He lowered his voice. "You are so well that I
think if I put my boat on the shore tonight, with food and extra clothing in
it, you might be able to row to that little island not far from the coast. It is
so near the coast that it has not been worth fortifying. Nobody lives on it
because in storm it is submerged. But this is not the season of storm. You
could live there until you saw a Korean fishing boat pass by. They pass
quite near the island because the water is many fathoms deep there'
The young man stared at him, slowly comprehending. Do I have to ? he
asked.'
"I think so", "Sadao said gently. "you understand - it is not hidden that
you are here."

What is Dr. Sadao's intention with the statement "... it is not hidden you are here."?

(a) to explain why he cannot stay there anymore.
(b) to remind him that he has tried to hide his presence.
(c) to explain that it is necessary and good for both of them.
(d) to assert that his house is not a hiding place.